A quality analyst wants to construct a control chart for determining whether four machines, all producing the same product, are in control with regard to a particular quality attribute. Accordingly, she inspected $1,000$ units of output from each machine in random samples, with the following results

Machine Total Defectives

#$143$

#$235$

#$349$

#$433$

What is the estimate of the process proportion of defectives?

Group of answer choices

$\mathrm{.}08$

$\mathrm{.}06$

$\mathrm{.}04$

$\mathrm{.}02$

$\mathrm{.}01$